On January 28, 2020 Avacta Group plc (AIM: AVCT), the developer of Affimer biotherapeutics and reagents, is reported that it has demonstrated initial proof-of-concept for its proprietary new class of drug conjugate, TMAC, in a pre-clinical animal model of cancer (Press release, Avacta, JAN 28, 2020, View Source [SID1234553627]). The study showed that AVA04-VbP outperformed Bavencio (Avelumab), a marketed anti-PD-L1 immunotherapy.
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Avacta’s tumour microenvironment activated drug conjugates (TMAC) are a ground-breaking new form of cancer immunotherapy, combining its Affimer biotherapeutics with chemotherapies in a single drug, using a linker (incorporating its proprietary pre|CISION substrate) that is designed to only release the chemotherapy in the tumour microenvironment through the action of an extracellular enzyme called FAPα. This mechanism overcomes the need to target an internalising cancer marker, as with conventional antibody drug conjugates (ADCs), and allows extremely potent chemotherapies to be combined with Affimer immune-checkpoint therapies. Combining pre|CISION technology with the Affimer platform is enabling Avacta to build a pipeline of novel and safe cancer therapies applicable to a broader range of cancer patients, including those who do not respond to existing immunotherapies.
AVA04-VbP combines an Affimer PD-L1 checkpoint inhibitor with an I-DASH chemotherapy warhead, addressing the acute systemic toxicity associated with I-DASH inhibitors by targeting the release of the drug warhead in the tumour microenvironment. The drug warhead induces a highly pro-inflammatory cell death, which in turn stimulates an immune response in the tumour, which is supported by the Affimer PD-L1/PD-1 signalling pathway blockade.
In a mouse syngeneic tumour model study, Avacta has shown that AVA04-VbP outperforms Bavencio; animals treated with AVA04-VbP showed a significant reduction in the rate of tumour growth with respect to those treated with Bavencio. A considerably higher level of the released I-DASH warhead was measured in the tumours compared with very low levels in the blood, indicating that healthy tissues are less exposed to the highly toxic warhead. This tumour targeting is central to the TMAC mechanism of action, and permits the use of the highly potent cancer-killing warheads.